1. Someone is absent from work and you're the person management chooses to cover for them.

2. You're awesome in the sort aisle and the supervisor over there requests you often.

3. Management hates you, found out you hate the sort aisle, and decided to put you there every chance they get.

Side-note: The sorters are preloaders too. Same with the guys in unload. Small-sort? If they're in there around 4am, they're all preloaders. The word describes the shift you work, not your position during the shift.